A library if cloned genes for plasma proteins has been prepared from human liver. m/RNA was fractionated by guanidinium thiocyanate extraction, and purified by affinity chromatography. cDNA was prepared using reverse transcriptase, and the cDNA was cloned in E-coli plasmid pBR322. Screening for specific genes has been initiated using synthetic polynucleotides prepared from the known amino acid sequences of plasma proteins and apolipoproteins. Several of the clones have been shown to contain the gene coding for human albumin. Current studies are underway to identify the clones containing genes which code for apolipoproteins A-I and E.